Various forms of suturing devices are known in the art, and those which utilize a curved needle and/or a cassette are particularly relevant to the present invention. For example, U.S. Pat. Nos. 4,027,608 and 4,235,177 to Arbuckle, 4,406,237 to Eguchi et al., 4,417,532 to Yasukata, and 4,440,171 to Nomoto et al. describe suturing devices that use a reciprocating curved needle and means for looping and/or securing a suture thread; U.S. Pat. No. 4,557,265 to Andersson, describes a suturing device and method for moving an arcuate needle in a closed path through opposite edges of a tissue incision to complete a suture; U.S. Pat. No. 4,899,746 to Brunk describes a suturing device incorporating a curved needle into a motor driven cassette; and, U.K. Patent No. 18,602 to Mitchell describes a suturing device utilizing an arcuate needle having two recesses on remote ends of the needle which are capable of being engaged by two mating tooth-like projections on the surface of a band.
There are various drawbacks, however, with the prior art. For instance, the apparatuses described in Arbuckle, Eguchi, Yasukata and Nomoto utilize a reciprocating needle. These devices, therefore, require an added mechanism for looping and/or securing the suture thread. The looping mechanism makes it impractical to change needles in these instruments quickly and efficiently during an operation because, for example, the looping mechanism would have to be repositioned to engage a different sized needle. In fact, it may not be possible to change needle sizes at all in some of these devices. Notwithstanding this problem, the instruments are also less efficient for tying a suture knot when compared to the automatic knot tying capabilities of the present invention. Moreover, these looping mechanisms unnecessarily increase the size of these suturing devices making them more difficult to operate, burdensome, and impractical for certain suturing procedures.
Instruments, such as those described in Andersson and Brunk, do not require the extra looping mechanism because they utilize a fully rotating arcuate suturing needle. Indeed, it is also possible to change needles quickly with the apparatus described in Brunk. These instruments, however, pose a potential health risk to surgery patients. These instruments utilize friction rollers to drive a curved suturing needle through biological tissue. The suturing needle, however, does not positively engage the friction rollers (and vice versa), and therefore, the needle is not prevented from slipping and embedding in a patient. This most likely occurs when the needle encounters a friction force from the tissue being sutured greater than the friction force of the rollers driving the needle. Needle slippage can be avoided by ensuring positive engagement of the needle with a needle driving mechanism similar to the apparatus described in Mitchell. However, even the Mitchell apparatus poses the same potential risk of embedding the needle in a patient where either tooth on the band fails to engage with its sole mating recess on the needle. Therefore, as evidenced by the prior art, there is a need for a suturing apparatus which overcomes these apparent problems.